Effects of Whole-Body Irradiation on the Microsomal Enzyme System and on Cytochrome P-450 of Rat Liver

Enzyme ◽  
1982 ◽  
Vol 27 (1) ◽  
pp. 19-24 ◽  
Author(s):  
Pierre Bernard ◽  
Jean-Marie Zajac
Keyword(s):  
Rat Liver ◽  
Enzyme System ◽  
Whole Body ◽  
Microsomal Enzyme ◽  
Cytochrome P 450

scholarly journals Characteristics of the rat liver microsomal enzyme system converting cholecalciferol into 25-hydroxycholecalciferol. Evidence for the participation of cytochrome p-450

1979 ◽  
Vol 184 (3) ◽  
pp. 491-499 ◽  
Author(s):  
T C Madhok ◽  
H F DeLuca
Keyword(s):  
Vitamin D ◽  
White Light ◽  
Microsomal Fraction ◽  
Enzyme System ◽  
Initial Reaction ◽  
Microsomal Enzyme ◽  
Reaction Velocity ◽  
Calcium And Phosphorus ◽  
Cytochrome P 450 ◽  
25 Hydroxycholecalciferol

Properties of the rat hepatic cholecalciferol 25-hydroxylase have been studied. An assay system has been developed in which 25-hydroxycholecalciferol production is linear for at least 2h in both homogenates and microsomal fraction. Furthermore, the initial reaction velocity is linearly related to the amount of liver tissue or microsomal fraction. This enzyme system also metabolizes an analogue of cholecalciferol, namely dihydrotachysterol 3, into 25-hydroxydihydrotachysterol 3. The 25-hydroxylase is in the microsomal fraction and not in mitochondria. It has a Km of 44 nM for cholecalciferol and 360 nM for dihydrotachysterol 3. Its activity is not altered by dietary concentrations of calcium and phosphorus. Vitamin D-deficient rats have higher activities of the hepatic 25-hydroxylase than those receiving 25 ng of cholecalciferol daily. The 25-hydroxylase is inhibited by metyrapone. An atmosphere of CO/O2 (9:1, v/v) inhibits the reaction by 87%. This inhibition is partially reversed by white light. Additionally, cholecalciferol and 25-hydroxycholecalciferol competitively inhibit aminopyrine demethylase. These results support the idea that the cholecalciferol 25-hydroxylase is a cytochrome P-450-dependent mono-oxygenase.

scholarly journals Ring-and N-hydroxylation of 2-acetamidofluorene by rat liver reconstituted cytochrome P-450 enzyme system

1975 ◽  
Vol 150 (3) ◽  
pp. 561-564 ◽  
Author(s):  
P D Lotlikar ◽  
K Zaleski
Keyword(s):  
Cytochrome C ◽  
Rat Liver ◽  
Enzyme System ◽  
Partial Purification ◽  
Hydroxylated Metabolites ◽  
Triton X ◽  
Cytochrome P 450 ◽  
Ring Hydroxylation ◽  
Hydroxylation Activity ◽  
Nadph Cytochrome C Reductase

The N- and ring-hydroxylation of 2-acetamidofluorene were studied with a reconstituted cytochrome P-450 enzyme from microsomal fractions of liver from both control and 3-methylcholanthrene-pretreated rats. Proteinase treatment and Triton X-100 solubilization were two important steps for partial purification of the cytochrome P-450 fraction. Both cytochrome P-450 and NADPH-cytochrome c reductase fractions were required for optimum N- and ring-hydroxylation activity. Hydroxylation activity was determined by the source of cytochrome P-450 fraction; cytochrome P-450 fraction from pretreated animals was severalfold more active than the fraction from controls. Formation of N-hydroxylated metabolites with reconstituted systems from both control and pretreated animals was greater than that with their respective whole microsomal fractions.

scholarly journals Effect of Whole-body X-irradiation on the Microsomal Drug-metabolizing Enzyme System in Rat Liver

1969 ◽  
Vol 10 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Shogo ICHII ◽  
Nagasumi YAGO ◽  
Shigeru KOBAYASHI ◽  
Saburo OMATA
Keyword(s):  
Rat Liver ◽  
Enzyme System ◽  
Whole Body ◽  
Drug Metabolizing Enzyme ◽  
X Irradiation ◽  
Metabolizing Enzyme

Effect of Whole-Body Irradiation on the Half-Life of Antipyrine and on the Microsomal Enzyme System of Rats

Enzyme ◽  
1983 ◽  
Vol 30 (3) ◽  
pp. 205-208
Author(s):  
Christian Thiriot ◽  
Francois Gaboriaud ◽  
Pierre Bernard
Keyword(s):  
Half Life ◽  
Enzyme System ◽  
Whole Body ◽  
Microsomal Enzyme
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